Currently the demands of automobiles, electronic devices, etc. are increasing since the related technologies have been rapidly developed. A global positioning system (GPS) has been widely used in the above-mentioned systems to meet the demands in different fields (e.g., navigation systems and portable devices).
A GPS receiver is used to receive signals from various satellites and to process the received signals in order to perform GPS positioning. Typically, GPS positioning can be performed in a certain time period after the GPS receiver is powered on. The GPS receiver has a parameter named time to first fix (TTFF) that can be defined as a time period for the GPS receiver to find satellites after the user first turns it on and to provide the first geographical location fix when the GPS receiver has been staying in a standby mode for hours or days. The TTFF can be relatively slow (e.g., a few minutes), e.g., in a weak-signal environment.